Re: [RFC PATCH 12/12] mm/damon/core: add trace point for damos stat per apply interval

Steven Rostedt
2025-11-24T15:15:13Z

On Sun, 23 Nov 2025 10:43:26 -0800
SeongJae Park <sj@kernel.org> wrote:

> --- a/mm/damon/core.c
> +++ b/mm/damon/core.c
> @@ -2256,6 +2256,19 @@ static void damos_adjust_quota(struct damon_ctx *c, struct damos *s)
> quota->min_score = score;
> }
>
> +static void damos_trace_stat(struct damon_ctx *c, struct damos *s)
> +{
> + unsigned int cidx = 0, sidx = 0;
> + struct damos *siter;
> +
> + damon_for_each_scheme(siter, c) {
> + if (siter == s)
> + break;
> + sidx++;
> + }
> + trace_damos_stat_after_apply_interval(cidx, sidx, &s->stat);
> +}
> +
> static void kdamond_apply_schemes(struct damon_ctx *c)
> {
> struct damon_target *t;
> @@ -2294,6 +2307,8 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
> (s->apply_interval_us ? s->apply_interval_us :
> c->attrs.aggr_interval) / sample_interval;
> s->last_applied = NULL;
> + if (trace_damos_stat_after_apply_interval_enabled())
> + damos_trace_stat(c, s);
> }
> mutex_unlock(&c->walk_control_lock);
> }

I wonder if the above would look better (and still produce good assembly)
if it was:

static inline void damos_trace_stat(struct damon_ctx *c, struct damos *s)
{
unsigned int cidx = 0, sidx = 0;
struct damos *siter;

if (!trace_damos_stat_after_apply_interval_enabled())
return;

damon_for_each_scheme(siter, c) {
if (siter == s)
break;
sidx++;
}
trace_damos_stat_after_apply_interval(cidx, sidx, &s->stat);
}

static void kdamond_apply_schemes(struct damon_ctx *c)
{
struct damon_target *t;
> @@ -2294,6 +2307,8 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
(s->apply_interval_us ? s->apply_interval_us :
c->attrs.aggr_interval) / sample_interval;
s->last_applied = NULL;
damos_trace_stat(c, s);
}
mutex_unlock(&c->walk_control_lock);
}

I have no real preference. I just think keeping the "if ()" statement out
of the main code as a more aesthetic look. But the above should be
equivalent in actual functionality.

-- Steve